Heater



FIG. 1 is a left side view of a heater showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a right side view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom view thereof; and,

FIG. 7 is a perspective view thereof. 

The ornamental design for a heater, as shown and described. 